micro-switch in 2.2T engine

PAT4 · 02-14-2005, 04:55 AM

Hi all,

Just bought a 2.2 T from 1970 three weeks ago. I just noticed that there was a micro switch in the engine compartment (arrowed)

Do you have an idea of what is it ?

vizail · 02-14-2005, 05:09 AM

Welcome to the Twilight Zone..

Get the aplicable Bentleys Repair Book and look at the wiring diagrams. If you don't have one call your library and check if they have a copy.

Good Luck

Vic

ChrisBennet · ChrisBennet's Garage

It's a closed throttle switch. There should be a lever that hits it when you take your foot off the gas.
-Chris

Early_S_Man · 02-14-2005, 08:35 AM

Vic, there is no Bentley book for 911s prior to 1978!!! If there was ... it would most likely say that steering , brake, axle, and electrical system maintenance on older vehicles is beyond the scope of this manual -- required legalese!!!

The speed switch [mounted on the electrical console next to rear defogger relay] and microswitch for carbureted engine applications are not documented in the factory service manual ... though undoubtedly designed to hold the throttle plates open a bit during overrun. It looks like a previous owner removed part of the linkage. There should also be a solenoid at the back of the left carburetor connected to the throttle linkage.

PAT4 · 02-14-2005, 11:06 AM

That's funny. The engine in the car has two Weber 40 IDA carbs AND the micro switch that is wired but do not operate ...

but I have an other 1970 2.2 T engine with two Zenith 40 TIN carbs WITHOUT the micro switch BUT with a part that can pull on the switch at idle throttle !

So I do not understand very well the electrical function at idle speed ...

jpnovak · 02-14-2005, 11:23 AM

It looks like that may be a different engine by the red shroud. What is the engine number/type? Was this an S MFI engine that was converted to carbs? Is that why the microswitch is not present?

PAT4 · 11:33 AM

The engine actually in the car, with the switch, is not a S one.
This engine is a 911.07 code with #6109095 (1970 2.2 T correct) not a MFI one ... but as you can see, a red fan cover normally dedicated to S models replaced the black one.

The other one, with Zenith carbs and no switch is a 911.03 code with 6111308 (1971 2.2 T correct)

targa911S · 02-14-2005, 12:20 PM

That switch is designed for MFI. It is a shut off switch to eliminate backfire on deceleration. PO must have junked the MFI and left the switch. Take it off...put it in you spare parts bin. Someday it will be worth a lot of money to an early MFI car owner. OR send it to me!

PAT4 · 02-14-2005, 01:13 PM

Targa911S, I do not agree with you.

This engine is not a MFI one but a T carbed one ! And I just found an exploded view of Zenith carbs that shows this switch (#11) !

This part appears to be OEM-90161310600 and costs $121.85 at PP catalog (oupsss) !

In fact, I do not know how it works and what's happen when pressed ...

vizail · 02-14-2005, 02:06 PM

Waren
You are right..! but there is a Book I beleive is an Old Chilton's. A big Fat Yellow and/or Black Book. I have seen it. I might be wrong about the name of the book but there is one. The service manual is a great resource. If you guys have the Original Factory Diagrams for those early car's make them available to the other Palicantees. I just receive a nice set of xerox copyes from a Senior Pelican BBS Mechanic. Everyone can help each other

Vic

Todd Simpson · 02-14-2005, 04:17 PM

That is the auxiliary enrichment micro-switch. It goes with Zenith carbs, not the Webers.

There's a solenoid on one carb and a connection line to the other carb. Mine never worked.

It's adjustment is detailed in the Haynes manual. It's function, however, is not.

I'm off to search for more helpful information.

project 911 · project 911's Garage

I've got both 70 & 71 2.2T motors with Zenith's, and this switch came on both. I can't remember for sure but I think it does work the enrichment solenoid on the passenger side carb. The following pic shows how it is contacted.

Early_S_Man · 02-14-2005, 05:59 PM

Targa911S,

A search of elecronic supplier catalogs found the following replacements for the MFI 'Microswitch' ... that turns out to be a standard USA size and mounting configuration dating back to the early 1960s:

Allied Electronics ia source for all of the following switches ... all in the $15 - $25 range.

http://www.alliedelec.com/

SelectaSwitch (mfg by Microswitch 15 Amp rating)-- BZ-2RQ1-A2

C&K Components, Inc. --
15 Amp rating - HBS2KCB4SJ055C-5
20 Amp rating - HL2KJC3J055C-5

Omron --
15 Amp rating - Z-15GQ-B7-K
20 Amp rating - A-20GQ-B7-K

All of the above have screw terminals and will need to have 1/4" quick-disconnect or 'Faston' terminal lugs attached to mate to the 911 wiring harness.

Guys,

The USA 2.2 Zenith-carbed engines were also equipped with a speed switch and a solenoid that I never found documented. My experience with a 1970 2.2 911T long ago [1972-3] provided the following data ... all of the following is recollection from long ago, and I can't find any factory documentation to confirm it

The microswitch, speed relay, and solenoid replaced a Solex pneumatic solenoid smog device used on VW Beetles and USA-only 911 carbureted engines for 1968 models ... that was rather unsatisfactory and difficult to adjust to operate properly ... it tended to make the carbs hang at 1800 rpm or so!

The operation of the 'electric' smog solution was as follows:

At engine speeds above 1500 rpm the speed relay connected +14 Volts to one side of the microswitch. If the throttles were closed [engine on 'overrun condition] ... the microswitch contacts were closed and the 'Hold-open' solenoid was operated ... opening the throttle plates a very slight amount on the order of 1/16", but not enough to open the microswitch. As the engine wound down below 1500 rpm, the speed switch removed +14 Volts from the microswitch, and the solenoid released, allowing the throttles to close fully and idle nomally.

ps ...

The 'carb' speed switch was slightly different from the MFI version, but C,M,A recommended use of the carb version on MFI engines if backfiring was a continued problem, particularly on 2.4S engines!

targa911S · 02-14-2005, 06:44 PM

Pat 4 and early Sman..slap me and call me stupid! I never knew the carbed T motor had such a switch. Ya learn somting every day. I remeber those VW switches ..they were a PITA.

PAT4 · 02-14-2005, 11:34 PM

Guys, I thank you a lot.

At this time all explanations goes in the same good way.

My car, with the 911-07 engine and Weber carbs and switch is a 1970 american 911 imported in Europe in 1997. I suppose that it was delivered with Zeniths and enrichment solenoid system.

My spare 911.03 engine with Zenith carbs was removed from a rusted french 911T that did not have enrichment systems (there was not emission control in 1970-1971 in France)